Activity of the Eta-Aquariid and Orionid meteor showers

Abstract

Aims. We present a multi-instrumental, multidecadal analysis of the activity of the Eta-Aquariid and Orionid meteor showers for the purpose of constraining models of 1P/Halley’s meteoroid streams. Methods. The interannual variability of the showers’ peak activity and period of duration is investigated through the compilation of published visual and radar observations prior to 1985 and more recent measurements reported in the International Meteor Organization (IMO) Visual Meteor DataBase, by the IMO Video Meteor Network and by the Canadian Meteor Orbit Radar (CMOR). These techniques probe the range of meteoroid masses from submilligrams to grams. The η-Aquariids and Orionids activity duration, shape, maximum zenithal hourly rates values, and the solar longitude of annual peaks since 1985 are analyzed. When available, annual activity profiles recorded by each detection network were measured and are compared. Results. Observations from the three detection methods show generally good agreement in the showers’ shape, activity levels, and annual intensity variations. Both showers display several activity peaks of variable location and strength with time. The η-Aquariids are usually two to three times stronger than the Orionids, but the two showers display occasional outbursts with peaks two to four times their usual activity level. CMOR observations since 2002 seem to support the existence of an ~12 yr cycle in Orionids activity variations; however, additional and longer term radar and optical observations of the shower are required to confirm such periodicity.

Modeling the past and future activity of the Halleyid meteor showers

“…Fig. 1 in Egal et al 2020), is presented in Appendix A. The appendix also reproduces the variations of the minimum orbit intersection distance (MOID) between the Earth and 1P/Halley around each node (cf.…”

“…Fig. 2 in Egal et al 2020), measuring the shortest Cartesian distance between the two osculating orbits when considering the pre-perihelion or the post-perihelion arcs of the comet's orbit.…”

“…In this work, we present the second part of our analysis of the Halleyid meteor showers. In Egal et al (2020), we documented the long-term activity (around several decades) of the η-Aquariids and Orionids. The showers' activity profiles, shapes, and year-to-year variations were defined through a compilation of visual meteor observations made since 1985, more recent measurements of the Canadian Meteor Orbit Radar (CMOR, cf.…”

“…The purpose of the present work is to apply the new numerical model of meteoroid stream evolution developed in Egal et al (2019) to the Halleyids. In particular, the long-term evolution of these streams can now be constrained by the 35 yr of observations reported in Egal et al (2020). Through extensive numerical simulations and the application of an adapted weighting solution to the ejected particles (see, e.g., Egal et al 2019), we constrained the model parameters using the η-Aquariid and Orionid intensity profiles and interannual variability since 1985.…”

“…Section 2 reviews the characteristics of 1P/Halley's nucleus, dust production activity, and dynamics that will serve as starting conditions for our numerical model. Section 3 presents a general description of the η-Aquariid and Orionid meteor showers, summarizing the A&A 642, A120 (2020) main conclusions of Egal et al (2020). A short historical review of prior Halleyid models is provided in Sect.…”